1. Field of the Invention
The present invention relates to a liquid discharge head including a discharge port for discharging a liquid as droplets, an individual liquid chamber communicating with the discharge port, and a piezoelectric body provided in correspondence with the individual liquid chamber, and a method of manufacturing the same. The liquid discharge head according to the present invention is applicable to an ink jet recording head for making prints on paper, cloth, leather, unwoven fabric, an over head projector (OHP) sheet, or the like, a patterning device or a coating applicator for attaching a liquid to a solid object such as a substrate or a plate material. Hereinbelow, the ink jet recording head is described as a representative example of the liquid discharge head.
2. Description of the Related Art
The ink jet recording device has an advantage in its capability of easily making prints in colors with high recording quality at high recording rate. The ink jet recording device further has many excellent advantages of being able to make prints on plain paper and capable of being reduced in size with ease. Because of having those advantages, the ink jet recording device is used as an image recording device such as a printer or a facsimile machine.
Examples of the ink jet recording device include an ink jet recording device which uses an ink jet head having an orifice plate for discharging a liquid. The orifice plate includes a flow path substrate provided with a flow path of a liquid, an individual liquid chamber provided to a first surface of the flow path substrate, a through path provided to pass through from the individual liquid chamber to a second surface of the flow path, and a discharge port which is bonded to the second surface of the flow path and communicates with the through path.
To discharge ink droplets, it is necessary to increase a pressure inside the individual liquid chamber. Examples of a pressure generating unit for generating the pressure include a pressure generating unit of bubble type, in which a heat generator provided inside the individual liquid chamber generates bubbles in a liquid, to thereby discharge the liquid as liquid droplets. Examples of the pressure generating unit also include a pressure generating unit of piezoelectric type in which a vibrating plate forming a part of the individual liquid chamber is deformed by a piezoelectric element to thereby form liquid droplets and a pressure generating unit of electrostatic type in which the vibrating plate is deformed by an electrostatic force to thereby discharge liquid droplets, which are commonly used. In the above-mentioned ink jet heads, the individual liquid chambers on the flow path substrate and pressure generation sources such as the piezoelectric elements are arranged at higher density and in larger numbers so as to attain high integration of the device, in order to meet demands of recent years for image formation in higher definition.
In order to comply with the above-mentioned demands, the above-mentioned ink jet head of piezoelectric type includes, for example, an electrode and a piezoelectric body which are formed through a film deposition technique over an entire surface of the vibrating plate, and the electrode and the piezoelectric body are processed by using a photolithographic technique so as to correspond to the individual liquid chambers. With the use of the film deposition technique and the photolithographic technique, an ink jet head having high density is attained. Also, use of a Si substrate and a metal member for the flow path substrate and the orifice plate enables to form the flow path and the discharge port with high accuracy.
In general, the piezoelectric body is provided to a position corresponding to each of the liquid discharge chambers and processed so as to have a width smaller than the width of the individual chamber. The piezoelectric body is completely removed by a film thickness thereof at a region which does not correspond to the individual liquid chamber. For processing those piezoelectric bodies, a dry etching technique using a chlorine-based gas has been introduced in recent years. According to the dry etching method, it is easy to control an etching rate and an etching shape as compared with a wet etching method which uses a fluorinated acid solution or another acid solution, which makes it easy to perform processing with high accuracy. Japanese Patent Application Laid-Open No. 2000-357826 discloses a technology for processing a layered structure of piezoelectric body elements having a Pt electrode through dry etching.
When the piezoelectric body is processed through dry etching, however, in a case of a structure disclosed in Japanese Patent Application Laid-Open No. 2000-357826 where the lower electrode is not patterned, the lower electrode functions as an etching stop layer for stopping the etching from progressing. When the piezoelectric body having the above-mentioned structure is processed, the lower electrode is also etched slightly, though it may hardly affect displacement performance or mechanical characteristics of the piezoelectric body. In particular, in a case where a Pt electrode is used as the lower electrode, a chlorine-based gas which is used for processing the piezoelectric body may also etch the surface of the Pt electrode, and the etched component of the Pt electrode may adhere to an end portion of the piezoelectric body thus processed. In the case where a metal adheres to an end portion of the piezoelectric body as described above, there arises a problem that the adhesion of metal may lead to a short-circuit between the upper and lower electrodes and a breakage of the piezoelectric body thin film.
Also, in a case where the lower electrode in the proximity of the piezoelectric body thin film which serves as a driving portion is exposed, there arises a problem that the upper and lower electrodes are short-circuited and the electrodes or the piezoelectric body thin film are damaged during operation.